After its successful launch by a Soyuz Rocket from Baiknour on 27 April and accurate insertion into its target orbit by the Fregat autonomous upper stage,
Platform commissioning includes the on-board verification of all primary and redundant platform subsystems, namely telemetry and telecommand, propulsion, power, thermal control, and attitude and orbit control.
Once the spacecraft platform has been commissioned, switch-on of the various payload elements can begin. First signal transmission is anticipated in the coming days.
Charging the batteries
Since the spacecraft had been running on battery power from just before liftoff - throughout the lengthy series of manoeuvres performed by Fregat to reach the intended orbit - the first tasks after separation from Fregat were to deploy the solar arrays and achieve Sun-pointing, so that battery charging could begin.
The first-choice method to turn the spacecraft for Sun-pointing is to use the reaction wheels.
Use of the reaction wheels for initial pointing is the first choice because, once they are operational, the supply of electricity from the solar arrays is essentially unlimited. However, due to the battery discharge that occurred during pre-orbital flight, the spacecraft operations manual only allows a restricted time for these manoeuvres to be accomplished.
Attitude and orbit control
GIOVE-B's reaction wheels were slow to respond and stable Sun-pointing was not achieved within the specified time period. As a consequence, around five hours after launch it was decided to put the satellite into safe mode, and Sun-pointing was achieved using small engines known as thrusters.
The initial underperformance of the reaction wheels was found to have occurred due to a mismatch between the on-board avionics software and the reaction wheel calibration data. This has now been corrected by the uploading of a software patch to the spacecraft, leading to nominal performance.
Use of the thrusters is the second-choice method because one of the factors determining the operational life of
The final units to be turned on will be the transmit chain consisting of